Many facilities and especially laboratories provide some method to ensure signal integrity when they have the occasion to operate high power equipment that uses electronics and sensors for controlling operations. These methods incorporate some forms of power distribution configuration, shielding, transformer isolation, etc., in an attempt to minimize noise and interference. Noise and interference can lower accuracy of measurements or lead to malfunctions especially with electromechanical systems that use low level logic and sensor signals to control operations. Some buildings are constructed with special ground planes that have their own isolated connection to earth ground with a conductive stake or stakes. Instrumentation and low level circuitry is then grounded to this special ground plane to minimize interference from building generated noise (e.g., starting motors or other inductive loads).
When trying to minimize coupling between high power signals and low power signals, it is advantageous to minimize the distance these signals run in parallel and to have the signals only cross at right angles when necessary. Likewise, it is advantageous to carefully construct grounding such that high level currents do not flow through ground traces to which low level circuits are grounded. These high currents generate voltage drops that become noise in the form of ground level voltage shifts. It is very difficult to provide a flexible way to construct facility power distribution so that equipment and control circuitry may be added while maintaining quality low level signal integrity and a high level of isolation from interference between functional units. Normally, modifying a facility with additional equipment essentially requires that the distribution network be likewise modified.
It is often necessary to provide a very low impedance ground path between multiple pieces of equipment. For high current applications (more than 1 kA for example), this means that any current carrying conductors, including a ground bus, must have a large cross-sectional area to keep the resistance between points below a few milliohms. For high frequency pulsed systems, the impedance can be dominated by inductance, so often wide thin conductors are used. Sometimes a thin sheet of copper several feet wide is used for both the shielding and a low impedance ground plane.
The resources expended to minimize signal cross talk in many pulsed power systems can represent a significant fraction of the overall system cost. Low level diagnostic signals are routinely carried by expensive shielded cables. Shielding on these cables is not effective in suppressing very low frequency noise. Specialized systems are implemented to test for the presence of undesirable ground loops. Battery operated isolation amplifiers are sometimes installed in desperation. Despite these efforts, considerable effort is frequently wasted tracking down and reducing unacceptable EMI pickup and low-level signals. With all these competing considerations, the usual result is a rat's nest of bulky cables on the floor and/or traveling across areas where it is necessary for people to walk.
Existing solutions using individually shielded cables, possibly routed through sheet steel enclosed trays, may be adequate for shielding out high-frequency EMI, but they do not have adequate skin depth for low frequencies below several kilohertz. Existing solutions do not address the issue of segregation of high current power cables from low level signal cables and do not provide a low resistance, low inductance star grounding path. Present cable distribution methods do not have good shielding characteristics extending from 50/60 Hz to higher frequencies and do not eliminate cable clutter and trip hazards while providing isolated and segregated shielding for low/high current cables.
There is, therefore, a need for a facility power distribution system that can be added to an existing facility while providing quality signal integrity and a low level of interference between modules that is scalable when adding equipment.